The present invention relates to improvements in methods and apparatus for installing a replacement pipeline section inside an existing underground conduit such as a pipeline section in need of repair or replacement. The present invention is particularly concerned with the installation of a replacement pipeline section within building sewers intersecting sewer mains, within other lateral pipelines, intersecting main pipelines, within pipeline sections that may include curves and abrupt bends, and within still other pipeline sections which are intersected by building sewers, the connections of laterals which would be difficult to locate after a new pipeline section is installed within the existing pipeline section.
Various processes and apparatuses have been suggested for repairing underground pipelines such as sewer lines and the like, with the existing pipeline remaining in place underground, by installing within the existing pipe a flexible membrane or liner of plastic or by inserting into the existing pipe a new plastic pipe.
In one known process, pipes are lined with a flexible plastic such as polyethylene. According to this process the liner is installed through insertion pits at intervals along the pipeline, making the process expensive.
According to another process, shown in, for example, U.S. Pat. Nos. 3,927,164 and 4,064,211 a flexible tube is turned inside out as it is inflated and blown into a pipeline section from one end of the section. This process is expensive because it requires special equipment, extensive heating and expensive materials.
The above mentioned processes and most others use a flexible or semi-flexible liner which is not capable of withstanding any appreciable external hydrostatic or earth pressures. Thus the existing pipe may not be properly repaired since if any part of it is broken away, the liner can possibly collapse from external pressure of any magnitude, such as pressures, for example, which exceed about 4 pounds per square inch.
Both Thomas et al U.S. Pat. No. 4,394,202 and Harper et al U.S. Pat. No. 2,794,758 also disclose processes of inserting flexible tubing into an existing pipeline as a lining membrane for that pipeline. Thomas discloses a method of attaching the flexible tubing to the existing pipeline using an expandable short section of adhesive-coated rigid plastic. Both the Thomas and Harper processes have the same drawbacks as previously mentioned with respect to other prior processes using flexible membrane material in that they lack the necessary hoop strength to withstand external earth and hydraulic pressures.
Others have suggested inserting a rigid tube inside the existing pipeline in need of repair. For example, in the published British application No. 2,084,686 an oversized round rigid plastic tube is flattened or otherwise reduced at the job site and then inserted cold and rigid into the existing pipeline through a large excavation at a manhole. After insertion, the plastic tube is expanded using heat and internal pressure. The plastic tube is expanded against the existing pipe.
According to British Patent No. 1,580,438, an existing underground pipe is lined with a plastic liner tube made of a plastic material such as polyethylene or polypropylene having a Plastic memory. The liner tube is manufactured in an out-of-round "U" shape to fit inside the existing pipe, then inserted in its out-of-round shape into the existing pipe, and then expanded against the existing pipe under heat and pressure to a round condition.
The published EPC Patent Application No. 0,000,576 suggests inserting a semi-rigid plastic tube insert inside an existing pipe. The semi-rigid plastic tube has sufficient hoop strength to withstand all or at least part of the external pressures that may be imposed upon it.
a. Repair of Crooked Pipelines and Pipelines With Access at Only One End
Most of the foregoing and other known prior art processes employing rigid or semi-rigid tubes for insertion in an existing underground pipe have a common drawback because of their rigidity or near rigidity they must be inserted in straight or nearly straight existing pipelines. This means, for example, with respect to underground sewer lines, such known processes are limited to use in sewer mains because they usually have straight pipeline sections between manholes. Most if not all of such known processes are not suitable for use in repairing the numerous building sewers that extend from the sewer mains to buildings. Frequently such laterals have curves or bends which a rigid or semi-rigid plastic pipe will not negotiate. Also, such laterals are normally not accessed by manholes at either end and therefore known lining or replacement pipe installation methods requiring manhole or other access at both ends are overly expensive. With most known underground replacement pipe installation processes, large excavations must be made at one end of the lateral to be relined or repaired to provide room for insertion of the straight rigid plastic replacement pipe. Such a large excavation adjacent to a building serviced by the lateral or at the other end where the lateral intersects the main is often impractical and usually expensive.
Furthermore, most known processes of relining or repairing existing underground pipelines require access to the pipeline section to be repaired at both ends of the section. This is not possible with a lateral, which by definition intersects a main line at a point that is usually not accessed by a manhole.
For the foregoing reasons, the known underground pipeline relining and repair Processes are simply not applicable to building sewers.
b. Repairing Sewer Mains
Another disadvantage in using known processes of repairing and relining existing pipeline sections intersected by building sewer lines using straight rigid or semi-rigid tubing is that once the tubing is in place in the existing pipeline section, it is very difficult to locate the exact positions where the service laterals intersect the main pipeline so that access openings can be cut in the replacement tubing to access the service laterals. This is especially true if the replacement tubing has sufficient thickness and therefore sufficient hoop strength to itself withstand typical hydraulic and earth pressures.
For the foregoing reasons, there is a need for improved methods, apparatus and tooling that would enable the repair of existing underlying pipeline sections, and especially building sewers and other pipeline sections having bends and curves, and pipeline sections that cannot be readily accessed from both ends of the pipeline section to be repaired.
Accordingly, primary objectives of the present invention are to provide the following:
1. A new and improved replacement pipeline product for installation in an existing underground conduit that is especially suitable for use in repairing and replacing existing building sewer lines that are not straight and main lines intersected by building sewers;
2. A new and improved method of manufacturing a repair and replacement pipeline product especially suitable for installation in existing underground conduits that are not straight or are intersected by lateral service lines;
3. A method of installing a new or replacement pipeline section in an existing underground conduit, and especially one that is not straight or that is intersected by building sewer lines;
4. Apparatus and tooling for manufacturing a replacement pipeline product as aforesaid;
5. Apparatus and tooling for installing a pipeline product as aforesaid in an existing underground conduit, and especially such a conduit that is not straight or that is intersected by lateral service lines; and
6. Apparatus and tooling for reforming a new or replacement thermoplastic pipe section installed in an existing underground conduit, and especially a building sewer, after the new or replacement pipe section has been inserted in a folded condition, by reforming it to a stable rounded shape within the existing conduit.